Early diagenetic dolomite cements; examples from the Permian Lower Magnesian Limestone of England and the Pleistocene carbonates of the Bahamas

In the Lower Magnesian Limestone dolospar occurs as isopachous rinds on the dolomitized micrite envelopes of hollow-centered allochems. Because compactional fractures penetrate both the allochem walls and the cement rinds, dolomite cementation is inferred to have predated any significant sediment accumulation. In the Great Abaco carbonates, limpid dolomite forms isopachous rinds around inter- and intragranular porosity, and is postdated by meteoric calcite cement. Both examples developed as a consequence of changes in pre-fluid chemistry from marine, to mixed meteoric-marine, to meteoric waters. Therefore, the presence of this cement type may point toward diagenetic environments resulting from marine regressions.--Modified journal abstract.